Screw compressor

ABSTRACT

Screw compressor having male- and female rotors for extremely high discharge pressures, the radial bearings and the supporting flanges enclosing the radial bearings tight-fitting adjoin the housing bores with their centres arranged on two parallel axes of the housing.

The invention relates to a design of screw compressor housing forcompressing a working fluid to an extremely high discharge pressurefeaturing two rotors with parallel axes, a male rotor having essentiallyconvex-shaped lobe flanks with at least four lobes and a female rotorhaving essentially. The male rotor has a drive-shaft end. Both rotorsare enclosed in a housing featuring at least an inlet port for passingof the working fluid into the lobes of the rotor pair and at least anoutlet port for discharge of the gas out of the lobes of the rotor pairdue to rotation of the rotors. The profile sections of the rotors haveshaft ends enclosed in radial bearings. The resulting axial forces ofthe rotors are being supported by axial bearings. The profile section ofthe rotors is extremely short, as described in U.S. Pat. No. 4,412,796,U.S. Pat. No. 3,787,154, U.S. Pat. No. 4,080,119, U.S. Pat. No.5,269,667. The axial length of the profile section of the rotor paircorresponds to approx. 1.4 the value of the axial lobe pitch whichcorresponds to the axial distance between two lobe-flank points ofneighbouring lobe flanks. Known compressors have several housingsections accommodating the bearings of the rotors. These housingsections are connected with each other by suitable means after havingbeen fixed at reference points. (U.S. Pat. No. 4,042,310, U.S. Pat. No.4,004,864, U.S. Pat. No. 4,084,405, U.S. Pat. No. 4,455,131, U.S. Pat.No. 4,597,726, US This configuration leads needs expensive alignment orit causes to impermissible inclined positions of the bearings, if thereare rotors with very short profile sections e.g. male rotor profilelength to outer diameter ratio of 0.35, as the axial distance betweenthe radial bearings arranged on both sides of the rotors is very short.

This has an impermissible impact on both the service life andload-carrying capacity of the bearings.

The feature of the invention is that all built-in components radialbearing housings enclosing the rotor profile and the rotor shafts arearranged in housing bores which centres are all arranged on two parallelaxes. Built-in components are supporting flanges for the radial bearingson the suction side, and for the radial bearings on the discharge side.The build in components are concentric arranged in supporting flanges.Due to the features of the invention the machining of the rotor—housingbores—is possible from one side of the rotor housing in concentricmanner which guarantee highest machining accuracy.

Due to this configuration, the bearings and the components likesupporting flanges adjacent to the bearings are guided at theirperiphery in the same housing concentric sections so that there will beno coaxial deviations from coaxial position of rotor caused by assembly.

Advantageously the assembling of supporting flanges, male and femalerotor and bearings is possible with out alignment and with outadjustment from one side of the housing.

The FIG. 1 shows cross section through the screw compressor regardingthe invention.

FIG. 2 shows a sample of a rotor pair consisting of male and femaleregarding the invention.

FIG. 3 shows the outer shape of a sample of a screw compressor regardingthe invention.

The screw compressor shown in FIG. 1 designed for compression of aworking fluid to a discharge pressure of 120 bar featuring two rotors, amale rotor 1 and a female rotor 2 with the male rotor 1 having adrive-shaft end 3, and both rotors are enclosed in a housing 8 featuringan inlet port 7 which is connected with a not shown suction flange forpassing of the working fluid into the cavities 12, 13 of the rotor pairand an outlet port 14 for discharge of the gas out of the cavities ofthe rotor pair due to rotation of the rotors. The profile sections 15 ofthe rotors have shaft shoulders 4 enclosed in radial bearings 5 on thesuction side and in radial bearings 9 on the discharge side with theresulting axial forces being supported by axial bearings 6. Thesupporting flanges 10 adjacent to the radial bearings are guided attheir periphery in the housing 8 so that there will arise no coaxialdeviations caused by assembly. The supporting flanges 10 are axiallyfixed by the end housing 11.

Regarding FIG. 2 the wrap angle 13 of male rotor 1 is about 100°. Causedby teeth ration 5:6 between male and female teeth index angle 12 betweenneighbouring teeth of male rotor 1 is 72°. The rotor length 17 is shortrelated to male rotor diameter 16.

In FIG. 3 is shown the economiser port 14 located on the part of thesurroundings of the rotor pair.

List of reference numerals used:

-   1 Male rotor-   2 Female rotor-   3 Drive-shaft end-   4 Shaft shoulders-   5 Radial bearing, suction side-   6 Axial bearing-   7 Inlet port-   8 Housing-   9 Radial bearing, discharge side-   10 Supporting flanges-   11 End housing-   12 teeth index angle-   13 wrap angle male rotor-   16 male rotor diameter-   17 rotor length

1. Screw compressors for extremely high discharge pressures up to 160bar featuring two parallel rotors, a male rotor and a female rotor withthe male rotor having a drive-shaft end for drive of the compressorlinguine or electric motor, and both rotors are enclosed in a housinghaving an inlet port and an outlet port, rotors with profile sectionsand shaft ends enclosed in radial bearings and with axial bearingswherein radial bearings and supporting flanges enclosing the radialbearings tight-fitting adjoin the housing bores the centres of which arearranged on two parallel axes of the housing.
 2. Screw compressoraccording to claim 1 wherein the outer races 15, 16 of the radialbearings on the compressor suction side directly adjoin the housing. 3.Screw compressor according to claim 1 wherein the outer races of theradial bearings on the discharge side tight-fitting adjoin concentricsupporting flanges.
 4. Screw compressor according to claim 1 wherein thesupporting flanges axially adjoin the end housing.